Soundboard ribs



SHOJI AKAGII SOUNDBOARD RIBS .May '13, 1969 Filed Dec. 1s. 1966 SheetFIG. 3v

M y 13, 1969 SHOJI'JAKAGI 4 souunaonmi mas Filed Dec. 15, 1966 Sheet of2 United States Patent 3,443,464 SOUNDBOARD RIBS Shoji Akagi,Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kabushiki Kaisha,Hamamatsu-shi, Shizuoka-ken, Japan Filed Dec. 15, 1966, Ser. No. 602,061Claims priority, application Japan, Dec. 25, 1965, 40/105,892 Int. Cl.GlOc 3/06 US. Cl. 84195 13 Claims ABSTRACT OF THE DISCLOSURE A pianosoundboard structure in which spaced apart ribs bounded to one surfaceof a soundboard are caused to have different acoustical characteristicsrespectively suitable for the operational frequencies of the respectiveparts of the soundboard to which the ribs are bonded, with theacoustical characteristics being varied by the use of different kinds ofwoods in different configurations for the ribs.

This invention relates to pianos and like musical instruments and moreparticularly to the soundboard structures of pianos and the like. Morespecifically, the invention concerns a new piano soundboard structurewhose sound transmission characteristics for tones of high frequency areremarkably improved by a novel selection of the composition andarrangement of the ribs of the soundboard structure.

As is known, the soundboard structure of a piano is fabricated bybonding a plurality of ribs in spaced-apart arrangement on the reverseor back surface of a soundboard and bonding one or more bridges forsupporting the strings of the piano to the front surface of thesoundboard. The soundboard is fabricated by joining a number ofstraight-grained boards with grains in their longitudinal direction inside-by-side arrangement, with adjacent longitudinal edges beingordinarily joined by bonding with an adhesive (usually glue).

The ribs are disposed perpendicularly or substantially perpendicularlyto the grain of the soundboard. Each rib is made of one of theconiferous woods such as fir and spruce (Picea jezoensis, Piceasitchensis, etc.) because of their excellent vibration transmissioncharacteristics and rigidity in the grain direction. However, whilespruce (including fir) is extremely good for transmission of vibrationsof a number of hundreds of cycles per second, they are not as good fortransmission of vibrations of higher frequencies of a number ofthousands of cycles per second.

Furthermore, since the vibration modes of high frequencies are extremelysmall, and since, in comparison therewith, the spacing of the ribs isexcessively large, the transmission of high-frequency vibrationsparticularly in the direction perpendicular to the grain of thesoundboard (i.e., in the direction of the ribs) is poor. As a result,pianos known heretofore have been deficient in sound volume (intensity)and tone color of tones at high frequencies (not in the sense only ofhigh and low of the fundamental frequencies of the tones, but in thesense of high and low of the frequencies including higher harmonics oflower tones).

It is an object of the present invention to improve the transmission ofvibrations of not only treble tones but ice also higher harmonics oflower tones and to improve tone color in a piano.

The foregoing object has been achieved by the present invention,according to which, briefly stated, there is provided a sound boardstructure in which the ribs are in direct contact with and bonded to onesurface of the soundboard and possess dilferent acousticalcharacteristics, with each rib having characteristics suitable for theoperational frequencies of that part of the sound board to which it isbonded.

One method for causing the ribs to have difierent acousticalcharacteristics is to use a hardwood for some of the ribs and a softerwood for the others. Another method is to vary the composition andconstruction of the ribs depending on whether they are to correspondoperationally to treble tones, medium tones, or base tones.

For example, it is possible to provide a rib of the above stated desiredcharacteristics by combining into a single rib a thin central member orlayer made of maple flanked on opposite sides with thin spruce sidemembers bonded thereto, with the three members forming a laminated orsandwich structure. While ribs of such special construction can beprovided over the entire area of the soundboard structure, the volume oftones of high frequency can be considerably increased by providing thesespecial ribs over only the regions of the soundboard structure of trebletones.

The nature, principle, utility, and details of the invention will bemore clearly apparent from the following detailed description when readin conjunction with the accompanying drawings, in which like parts aredesignated by like reference numerals.

In the drawings:

FIG. 1 is a perspective view showing, principally, the reverse side of ageneral example of a soundboard structure of a grand piano;

FIG. 2 is an enlarged, fragmentary perspective view showing one part ofthe soundboard structure shown in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line IIIIII inFIG. 2;

FIG. 4 is a perspective view showing, principally, the reverse side of asoundboard structure illustrating one example of embodiment of theinvention;

FIG. 5 is an enlarged, fragmentary perspective view showing anotherexample of embodiment of the invention;

FIG. 6 is a fragmentary sectional view taken along the line VI-VI inFIG. 5;

FIG. 7 is a planar view of the reverse side of one example of asoundboard structure according to the invention for a grand piano ofsemi-concert type; and

FIG. 8 is a planar view of the reverse side of an example of asoundboard structure according to the invention for an upright piano.

As conducive to and as a basis for a full understanding of the natureand utility of the present invention, the following brief considerationof the soundboard structure of a piano of general type with respect toan example thereof as illustrated in FIGS. 1, 2, and 3 is firstpresented, principally for the purpose of comparison,

As illustrated in FIG. 1 and as mentioned briefly hereinbefore, thesoundboard structure of a piano, in general, has as its principalcomponent a single substantially flat soundboard 11 made up of severalsoundboard elements in side-by-side arrangement with adjacentlongitudinal edges glued or adhesively bonded together, with eachelement being a piece of good-quality, straight-grained Wood with itsgrain in its longitudinal direction. The soundboard 11 is provided onits reverse or back side with a plurality of ribs 12 bonded thereto inspacedapart, substantially parallel arrangement with their longitudinaldirections perpendicular or substantially perpendicular to the grain ofthe soundboard 11, i.e., to the longitudinal direction of the soundboardelements 10. The soundboard 11 is provided on its front side with abridge device (as shown in FIGS. 7 and 8) bonded thereto in a directionsubstantially diagonal to the grain of the soundboard 11, with thebridge device 15 having the function of supporting the strings of thepiano.

The number of ribs 12 used for each soundboard differs with the type ofpiano, it being the common practice to use l7 ribs in a full-concertgrand piano, 15 ribs in a semi-concert grand piano, 13 ribs in a smallgrand piano, and 11 ribs in an upright piano. Heretofore, it has beenthe common practice to fabricate all of the ribs for any one soundboardfrom the same kind if wood, particularly spruce (including fir) beingordinarily selected because of its good rigidity and sound transmissioncharacteristics in its grain (longitudinal) direction.

However, when all of the ribs are made from the same kind of Wood, thesound transmission characteristics of the soundboard structure,especially the tone volume and tone color at high frequencies, becomedeficient.

The present invention contemplates the elimination of this deficiency byfabricating each rib in a manner such that it will have characteristicssuitable for operational frequencies of that part of the soundboard towhich it is bonded, as described more fully hereinbelow with respect topreferred embodiments of the invention.

In one embodiment of the invention as shown in FIG. 4, ribs 13 made ofspruce as heretofore and ribs 14 made of hardwood such as maple, beech,and birch are bonded to a soundboard 11. It will be seen that the ribsare in direct contact with the surface of the board 11 and the hardwoodribs 14 are interposed alternately between every two adjacently disposedspruce ribs 13. All of the ribs in the treble region are hardwood ribs14.

In order to fabricate the ribs partially of hardwood, it is possible tofabricate a certain number of the ribs among the total number of ribsentirely of a hardwood as indicated in FIG. 4. Alternatively, it is alsopossible to construct composite ribs each having, as viewed in crosssection, one part made of a hardwood and the remaining part made of asoftwood as shown in FIGS. 5 and 6. That is, in the example illustratedin FIGS. 5 and 6, the central part of a layer 13a of the rib 13 is madeof a hardwood such as maple, beech or birch and the flanking parts orlayers 1311 are made of a softer wood such as spruce, whereby alaminated or so-called sandwich construction is produced.

It has been found that excellent results can be obtained by making thewidth in the horizontal direction as viewed in FIG. 6) of the centralpart made of a hardwood equal to from /s to /3 of the total width of thecompleted rib. Accordingly, if the widths of the two flanking parts 13bare equal, the desirable ratio of the widths (in sequence from one sideto the other) is from 2:1:2 to 1:1:1.

Ribs of the above described construction may be provided, for example,at only the treble region of the soundboard 11 or may be partly providedover the entire soundboard. In this case the lower-frequency sounds aretransmitted by the softwood, and the higher-frequency sounds aretransmitted by the hardwood. Therefore, according to the presentinvention it is possible to increase the tone volume over a widerfrequency range than was heretofore possible.

In a specific example of embodiment of the invention as illustrated inFIG. 7, of the ribs 12 on the reverse side of a soundboard structure ofa grand piano, three (2 to 5 4 are suitable) ribs in the treble regionof the soundboard are made of hardwood such as maple, beech, and birchor are laminated composite ribs of softer wood and hardwood asillustrated in FIG. 6. The remaining ribs, i.e., the ribs at the mediumand bass regions are made of a softer wood such as spruce.

Another specfic embodiment of the invention as applied to an uprightpiano is illustrated in FIG. 8 showing the back of the soundboardstructure. Two of the ribs 12a and 12b in the treble region arelaminated composite ribs as illustrated in FIG. 6.

The soundboard structures illustrated in FIGS. 7 and 8 are provided withbridge devices 15. In the example shown in FIG. 7, the bridge device isin the form of a continuous curved member (rertangular in crosssection), while, in the example shown in FIG. 8, it is divided into twoparts. In either case, the main portion of the bridge device is in asubstantially parallel direction relative to the grain direction of thesoundboard.

When the ribs in a soundboard structure are made partially of hardwood,and the remaining parts of the ribs are made of spruce as describedabove, the vibrations of medium and low frequencies are transmitted wellby the spruce, while the vibrations of high frequencies are transmittedwell by the hardwood. Therefore, by the use of the piano soundboardaccording to the invention, it is possible to obtain high tone volumeand, moreover, excellent tone color even at high frequencies.

While the invention has been described above with respect to examples ofapplication thereof to grand pianos, it will be obvious that theinvention can be applied with equal facility and effectiveness also toupright pianos.

What I claim is:

1. A piano soundboard structure comprising a soundboard having oppositesurfaces, a plurality of ribs in direct contact with one surface of thesoundboard and being bonded to such surface, and a bridge device bondedto the opposite surface of the soundboard, certain of said ribs being ofhardwood, and the remainder of said ribs of softer wood.

2. The piano soundboard structure as claimed in claim 1, in which saidhardwood is selected from among maple, beech and birch.

3. The piano soundboard structure as claimed in claim 1, in which saidcertain ribs are of laminated bonded construction consisting ofelongated layers of hardwood and elongated'layers of softer wood.

4. The piano soundboard structure as claimed in claim 3, in which saidcertain ribs consist of a central layer of hardwood sandwiched betweenouter side layers of softer wood.

5. The piano soundboard structure as claimed in claim 4, in which saidcertain ribs consist of a central layer of maple sandwiched betweenouter side layers of spruce.

6. The piano soundboard structure as claimed in claim 4, in which thethickness of the central layer of hardwood is from /5 to /3 of the totalwidth of the rib.

7. The piano soundboard structure as claimed in claim 1, in which saidcertain ribs of hardwood are provided at the treble region of thesoundboard.

8. The piano soundboard structure as claimed in claim 7, in which saidhardwood is selected from maple, beech and birch.

9. The piano soundboard structure as claimed in claim 7, in which saidcertain ribs provided at the treble region are from 2 to 5 inclusive ofribs at the highest treble region.

10. The piano soundboard structure as claimed in claim 7 in which saidcertain ribs are of laminated bonded construction consisting of anelongated central layer of hardwood and elongated outer side layers ofsofter wood.

11. The piano soundboard structure as claimed in claim 10 in which saidcertain ribs of laminated bonded construction consists of a centrallayer of maple sandwiched between outer side layers of spruce.

5 12. The piano soundboard structure as claimed in claim 10 in whichsaid certain ribs of laminated bonded construction are two ribs providedat the treble region of the soundboard. 13. The piano soundboardstructure as claimed in claim 1 in which said ribs of hardwood and saidribs of softer 5 wood are disposed in alternate relationship in themediumtone region and bass region of the soundboard.

6 References Cited UNITED STATES PATENTS 2/1873 Steinway 84-195 5/1927Mehlin 84-192 RICHARD B. WILKINSON, Primary Examiner.

L. R. FRANKLIN, Assistant Examiner.

